This project is a collaborative effort that seeks the development of new computer-based support systems that provide the radiotherapist and medical physicist in the field of radiation therapy treatment planning with new tools that will help to make three dimensional treatment planning a routine activity. The contractor will participate as a member of Collaborative Working Group and will participate in the design development and evaluation of computer based tools that accomplish the specific tasks: (a1) Automatically and rapidly extract anatomical features from multiple CT images to construct three dimensional volumes that are needed for the definition of critical structures in the treatment planning process. (a2) Assist physicians in the tumor localization process on the CT scans for treatment planning purposes. (a3) Assist the physician in the generation of treatment volume contours given the tumor volume localization information. (a4) Make "first-guess" choices for an optimal treatment plan. (a5) Present alternative "optimal" plans for the radiotherapist using the full capabilities of a three dimensional treatment planning system. (a6) Provide means for rapidly and interactively comparing digitally produced portal images with CT reconstructions that represent the patient's anatomical configuration in the treatment position.